Commit d6af2ed2 authored by Wei Hu's avatar Wei Hu Committed by Lorenzo Pieralisi
Browse files

PCI: hv: Fix a timing issue which causes kdump to fail occasionally 

Kdump could fail sometime on Hyper-V guest because the retry in
hv_pci_enter_d0() releases child device structures in hv_pci_bus_exit().

Although there is a second asynchronous device relations message sending
from the host, if this message arrives to the guest after
hv_send_resource_allocated() is called, the retry would fail.

Fix the problem by moving retry to hv_pci_probe() and start the retry
from hv_pci_query_relations() call.  This will cause a device relations
message to arrive to the guest synchronously; the guest would then be
able to rebuild the child device structures before calling
hv_send_resource_allocated().

Link: https://lore.kernel.org/r/20200727071731.18516-1-weh@microsoft.com


Fixes: c81992e7 ("PCI: hv: Retry PCI bus D0 entry on invalid device state")
Signed-off-by: default avatarWei Hu <weh@microsoft.com>
[lorenzo.pieralisi@arm.com: fixed a comment and commit log]
Signed-off-by: default avatarLorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: default avatarMichael Kelley <mikelley@microsoft.com>
parent b3a9e3b9

drivers/pci/controller/pci-hyperv.c

+37 −34
Original line number Diff line number Diff line
@@ -2759,10 +2759,8 @@ static int hv_pci_enter_d0(struct hv_device *hdev) 
	struct pci_bus_d0_entry *d0_entry;

	struct hv_pci_compl comp_pkt;

	struct pci_packet *pkt;

	bool retry = true;

	int ret;



enter_d0_retry:

	/*

	 * Tell the host that the bus is ready to use, and moved into the

	 * powered-on state.  This includes telling the host which region
@@ -2789,38 +2787,6 @@ static int hv_pci_enter_d0(struct hv_device *hdev) 
	if (ret)

		goto exit;



	/*

	 * In certain case (Kdump) the pci device of interest was

	 * not cleanly shut down and resource is still held on host

	 * side, the host could return invalid device status.

	 * We need to explicitly request host to release the resource

	 * and try to enter D0 again.

	 */

	if (comp_pkt.completion_status < 0 && retry) {

		retry = false;



		dev_err(&hdev->device, "Retrying D0 Entry\n");



		/*

		 * Hv_pci_bus_exit() calls hv_send_resource_released()

		 * to free up resources of its child devices.

		 * In the kdump kernel we need to set the

		 * wslot_res_allocated to 255 so it scans all child

		 * devices to release resources allocated in the

		 * normal kernel before panic happened.

		 */

		hbus->wslot_res_allocated = 255;



		ret = hv_pci_bus_exit(hdev, true);



		if (ret == 0) {

			kfree(pkt);

			goto enter_d0_retry;

		}

		dev_err(&hdev->device,

			"Retrying D0 failed with ret %d\n", ret);

	}



	if (comp_pkt.completion_status < 0) {

		dev_err(&hdev->device,

			"PCI Pass-through VSP failed D0 Entry with status %x\n",
@@ -3058,6 +3024,7 @@ static int hv_pci_probe(struct hv_device *hdev, 
	struct hv_pcibus_device *hbus;

	u16 dom_req, dom;

	char *name;

	bool enter_d0_retry = true;

	int ret;



	/*
@@ -3178,11 +3145,47 @@ static int hv_pci_probe(struct hv_device *hdev, 
	if (ret)

		goto free_fwnode;



retry:

	ret = hv_pci_query_relations(hdev);

	if (ret)

		goto free_irq_domain;



	ret = hv_pci_enter_d0(hdev);

	/*

	 * In certain case (Kdump) the pci device of interest was

	 * not cleanly shut down and resource is still held on host

	 * side, the host could return invalid device status.

	 * We need to explicitly request host to release the resource

	 * and try to enter D0 again.

	 * Since the hv_pci_bus_exit() call releases structures

	 * of all its child devices, we need to start the retry from

	 * hv_pci_query_relations() call, requesting host to send

	 * the synchronous child device relations message before this

	 * information is needed in hv_send_resources_allocated()

	 * call later.

	 */

	if (ret == -EPROTO && enter_d0_retry) {

		enter_d0_retry = false;



		dev_err(&hdev->device, "Retrying D0 Entry\n");



		/*

		 * Hv_pci_bus_exit() calls hv_send_resources_released()

		 * to free up resources of its child devices.

		 * In the kdump kernel we need to set the

		 * wslot_res_allocated to 255 so it scans all child

		 * devices to release resources allocated in the

		 * normal kernel before panic happened.

		 */

		hbus->wslot_res_allocated = 255;

		ret = hv_pci_bus_exit(hdev, true);



		if (ret == 0)

			goto retry;



		dev_err(&hdev->device,

			"Retrying D0 failed with ret %d\n", ret);

	}

	if (ret)

		goto free_irq_domain;